Refrigeration appliance comprising a plurality of shelves

ABSTRACT

A refrigeration appliance includes at least two compartments designed for different storage temperatures to define a first compartment and a second compartment, with the storage temperature of the first compartment exceeding the storage temperature of the second compartment. A refrigerant circuit has a first branch which is routed via an evaporator of the first compartment and a second branch which is routed via an evaporator of the second compartment. The evaporator of the second compartment includes a first refrigerant conduit which is connected upstream of the evaporator of the first compartment in the first branch, and a second refrigerant conduit which is associated with the second branch.

The present invention relates to a refrigeration appliance, in particular a domestic refrigerator, comprising at least two compartments designed for different storage temperatures. Such appliances, also known as fridge/freezers, generally have a normal refrigeration compartment and a freezer compartment; a zero degree compartment or cold-storage compartment, for example, may also be present.

In simple appliances of this kind, evaporators assigned to respective compartments are connected in series in a refrigerant circuit. The distribution of refrigerating power to the compartments is fixed by the design of the appliance and is e.g. dependent on the order of the evaporators in the refrigerant circuit and their relative sizes. If the refrigerating power distribution corresponds to the refrigeration requirement of the compartments, usable temperatures are attained in a plurality of compartments even if refrigerant circuit control is only possible on the basis of the temperature measured in one of the compartments. However, if—e.g. because of unusual ambient temperatures—the ratio of the refrigeration requirement of the compartments shifts, this will result in inadequate or excessive cooling of the compartment.

In a refrigerant circuit with evaporators connected in series, the evaporator of the normal refrigeration compartment is usually disposed upstream of that of the freezer compartment. Refrigerant which evaporates in the evaporator of the normal refrigeration compartment in an idle phase of the circuit forces colder refrigerant in the freezer compartment evaporator downstream, resulting in unwanted heat input to the freezer compartment.

In order to be able to control the temperatures of two or more compartments in a refrigerator independently of one another, it is necessary to assign each compartment a refrigerant circuit of its own, which involves considerable cost, or to create a branched refrigerant circuit wherein the evaporators of different compartments are disposed in a plurality of mutually parallel branches of the refrigerant circuit, a valve being provided for optionally applying refrigerant to one or other branch.

Although this approach is less expensive than having separate refrigerant circuits, interactions between the branches occur which impair the efficiency of the refrigerant circuit. If, for example, refrigerant has been applied for some time to the evaporator of a cold compartment such as a freezer compartment, and the compartment has reached a low temperature at which the supply of refrigerant is terminated, liquid refrigerant is stored for a long period in the evaporator of said compartment without circulating. If immediately after termination of the refrigerant supply to the cold compartment a warmer compartment such as a normal refrigeration compartment has to be cooled, only a small amount of refrigerant is available for that purpose. Only low pressures are attained in the refrigerant circuit, and the efficiency is poor. It does not improve until a large portion of the refrigerant in the evaporator of the cold compartment evaporates again and is returned to the circuit. However, this requires an increase in the temperature in the colder compartment, i.e. operating pressures of the refrigerant which allow efficient operation are only attained if, shortly thereafter, cooling is again required in the colder compartment. The efficiency of the refrigerant circuit is therefore impaired for a considerable portion of its operating time.

The object of the present invention is to create a refrigeration appliance having at least two compartments designed for different storage temperatures, whereby independent cooling of the compartments can be achieved with good efficiency using a refrigerant circuit of simple design.

In the case of a refrigeration appliance having at least two compartments and a branched refrigerant circuit, a first branch of which is routed via an evaporator of the warmer compartment and a second branch via an evaporator of the colder compartment, this object is achieved by the evaporator of the colder compartment comprising two refrigerant conduits, a first of which in the first branch is connected upstream of the evaporator of the warmer compartment, whereas the second conduit is associated with the second branch.

This design makes it possible for refrigerant to be applied to the second branch only if applying refrigerant to the first branch would result in undercooling of the warmer compartment. On the one hand, this reduces the frequency with which refrigerant is applied to the second branch and as a result of which liquid refrigerant may remain in the evaporator at the end of the said application; on the other hand, as the second branch only needs to be used when there is a risk of undercooling of the warmer compartment, there is low probability of cooling being required in the warmer compartment shortly after refrigerant is applied to the second branch and of only a suboptimal amount of refrigerant being available for application to the first branch.

In order to minimize the amount of liquid refrigerant which can remain the second branch, the volume of the second branch is preferably selected smaller than that of the first.

According to an alternative embodiment of the invention, it is provided that the volume of the second branch is selected greater than that of the first branch. As a result, the colder compartment is cooled much faster.

Particularly if the volume of the second branch is smaller than that of the first, the problem may arise that refrigerant does not evaporate completely as it passes through the second branch. If liquid refrigerant reaches the compressor of the refrigerant circuit, it cannot operate correctly and there is a risk of it being damaged. A refrigerant reservoir is therefore expediently provided in a low pressure region of the refrigerant circuit in order to catch any liquid refrigerant before it reaches the compressor.

The refrigerant reservoir is preferably disposed downstream of a junction of the two branches, so that liquid refrigerant that has possibly collected therein can be evaporated and returned to the circuit even if refrigerant is circulating only in the first, but not in the second branch.

The refrigerant reservoir is preferably flowed through in a rising direction, so that refrigerant stored therein cannot escape in liquid form.

The two conduits are preferably distributed evenly over the surface of the evaporator of the colder compartment in order to achieve a uniform cooling effect, regardless of whether the evaporator is cooled by refrigerant circulating in the first or in the second branch.

The two branches preferably each have a throttle point. Thus a valve for applying refrigerant to either of the two branches can be disposed in a high pressure region of the refrigerant circuit, and a compact and inexpensive valve with a small flow cross section can be used.

The length of the first refrigerant conduit on the evaporator of the colder compartment is preferably calculated shorter than the length of the second refrigerant conduit or of the same length as the second refrigerant conduit.

Further features and advantages of the invention will emerge from the following description of exemplary embodiments with reference to the accompanying drawings in which:

FIG. 1 schematically illustrates a refrigerant circuit in a fridge-freezer.

FIG. 1 shows a highly schematized front view of the carcass 1 of a refrigeration appliance comprising a freezer compartment 2 located below a normal refrigeration compartment 3. Disposed in both compartments 2, 3 are evaporators 4, 5, the evaporator (5) provided in the normal refrigeration compartment (3) being implemented as a plate-type evaporator and disposed on the back wall of said refrigeration compartment, while the evaporator (4) disposed in the freezer compartment (2) can be implemented e.g. as a finned-type evaporator. The evaporators 4, 5 are connected into a refrigerant circuit additionally comprising a compressor 6, a condenser 7, a directional valve 8, two capillaries 9, 10 and a vapor dome 11.

At the directional valve 8, the refrigerant circuit forks into two branches. A first branch 15 comprises the capillary 9, a conduit 16 on the evaporator 4 of the freezer compartment 2 and, adjoining thereto downstream, a conduit 17 on the evaporator 5 of the normal refrigeration compartment 3. The second branch 18 comprises the capillary 10 and a conduit 19 on the evaporator 4. The two branches meet again at a point 20 upstream of the vapor dome 11.

The two conduits 16, 19 of the evaporator 4 are approximately of the same length and run essentially side by side over the entire surface area of the evaporator 4, so that the latter is essentially uniformly cooled, regardless of which of the two branches 15, 18 has refrigerant circulating.

A control circuit 12 controls the operation of the compressor 6 and of the directional valve 8 on the basis of temperatures detected by means of two sensors 13, 14 in the compartments 2, 3. For the two compartments 2, 3 there is predefined in each case a range in which the measured temperatures must move. If, in one of the compartments, the temperature measured is above the range, the compressor 6 is put into operation.

Let us first consider the case that the compressor 6 is turned on because the temperature measured in the freezer compartment 2 is above the upper limit of the permissible range. If at the same time the temperature measured in the normal refrigeration compartment is within the permissible range, the directional valve 8 is actuated in order to supply the branch 15 with refrigerant. As the volume of the branch 18 is small compared to that of the branch 15, at best a small amount of liquid refrigerant can be stored in the branch 18 at this time. The circulating refrigerant as a proportion of the contents of the refrigerant circuit is therefore high, and, accordingly, a high pressure can be achieved at the output of the compressor 6, which enables highly efficient cooling to take place.

Any liquid refrigerant stored in the vapor dome 11 when the compressor 6 is started up is heated by through-flowing warm, gaseous refrigerant from the evaporator 5 so that it likewise evaporates and is available to the circuit shortly after the compressor 6 is activated.

As the refrigerant circulates through both evaporators 4, 5, the normal refrigeration compartment 3 is also cooled. If its temperature reaches the lower limit of its permissible range before this occurs in the freezer compartment 2, the control circuit 12 switches over the directional valve 8 so that refrigerant is applied only to the freezer compartment evaporator 4 via the branch 18. As the flow rate of the compressor 6 is designed to supply enough refrigerant to ensure that sufficient liquid refrigerant to cool the normal refrigeration compartment 3 reaches the evaporator 5 when refrigerant is applied to the branch 15, it can be easily understood that not all refrigerant in the conduit 19 evaporates as it passes via the branch 18. A residual amount of liquid refrigerant which leaves the evaporator 4 again is trapped in the vapor dome 11 so that it does not reach the compressor 6. The vapor dome 11 can be simply implemented in the form of a rising tube section that is more capacious than adjoining refrigerant conduit sections, so that gaseous refrigerant entering the vapor dome 11 from below can bubble through any liquid refrigerant contained therein and exit again at an upper end without entraining the liquid refrigerant. The vapor dome 11 is disposed in a thermally insulated manner so that refrigerant passing through it from the evaporator 5 is the main source of evaporation heat for stored liquid refrigerant.

The case can naturally also arise that the temperature in the normal refrigeration compartment 3 rises above the upper limit of the permissible range, while the temperature in the freezer compartment 2 is within the permissible range. In this case, cooling of the normal refrigeration compartment 3 without simultaneous cooling of the freezer compartment is not possible with the refrigerant circuit shown in FIG. 1. However, this is in no way disadvantageous if the evaporators 4, 5 are dimensioned such that, during operation of the branch 15, the portion of the refrigerating power allocated to the normal refrigeration compartment 3 is greater than that corresponding to its average requirement. If the compressor 6 is always switched off again when the temperature in one or other of the two compartments 2, 3 reaches the lower limit of the assigned range, it is possible to ensure sufficient cooling of the normal refrigeration compartment 3 and also to eliminate undercooling in both compartments.

As the evaporator 5 of the normal refrigeration compartment is connected downstream of the freezer compartment evaporator 2 in the branch 15, an unwanted heat input to the freezer compartment due to refrigerant evaporating in the evaporator 5 when the compressor is switched off is eliminated. 

1-9. (canceled)
 10. A refrigeration appliance, comprising: at least two compartments designed for different storage temperatures to define a first compartment and a second compartment, with the storage temperature of the first compartment exceeding the storage temperature of the second compartment; and a refrigerant circuit having a first branch routed via an evaporator of the first compartment and a second branch routed via an evaporator of the second compartment, wherein the evaporator of the second compartment comprises a first refrigerant conduit which is connected upstream of the evaporator of the first compartment in the first branch, and a second refrigerant conduit which is associated with the second branch.
 11. The refrigeration appliance of claim 10, constructed as a domestic refrigerator.
 12. The refrigeration appliance of claim 10, wherein the second branch has a volume which is smaller than a volume of the first branch.
 13. The refrigeration appliance of claim 10, wherein the second branch has a volume which is larger than a volume of the first branch.
 14. The refrigeration appliance of claim 10, wherein the first refrigerant conduit of the evaporator of the second compartment has a length which is calculated shorter than a length of the second refrigerant conduit or of a same length as the second refrigerant conduit.
 15. The refrigeration appliance of claim 10, further comprising a refrigerant reservoir provided in a low pressure region of the refrigerant circuit.
 16. The refrigeration appliance of claim 15, wherein the refrigerant reservoir is disposed downstream of a junction of the first and second branches.
 17. The refrigeration appliance of claim 15, wherein the refrigerant reservoir is flowed through in a rising direction.
 18. The refrigeration appliance of claim 10, wherein the first and second refrigerant conduits are evenly distributed over the evaporator of the second compartment.
 19. The refrigeration appliance of claim 10, wherein each of the first and second branches has a throttle point. 